A LOT of Iolanthe was patterned on Wagner...but it was parody, so it wasn’t really stealing.
Also, the Mikado has hints of “Madame Butterfly”, and “I am a Courtier Grave and Serious” from the Gondoliers lifts verbatum a finger exercise from the Hanon Piano book.
I love doing parodies.
The MIKADO has less than NOTHING at all to do with Madam Butterfly!
Sullivan, being his petulant, nasty, self absorbed, pompous self, turned down Gilbert's latest, as being "too Topsy Turvy"/MAGIC LOZENGE. He had been on holiday in Europe, never wrote back to Gilbert, and when he got back, threw a hissy fit.
They had a contract, Carted demanded an operetta.
Gilbert balked and they all went home in a huff!
At that time, there was a Japanese exhibit going on in London. EVERYONE WAS GOING TO IT! Gilbert went with his wife. And all of a sudden ( the "story goes that he bought a Japanese sword, had it hung, and then the sword fell of the wall and hit him....true or not, it's the "STORY" ) and the light bulb went off and dear Schwenck sat down and began to write THE MIKADO! :-)
That's the operetta that my parents' troupe did on T. V.! I watched my parents rehearse at home, and I can do every single gesture/fan move/etc. from that operetta. :-)
I have a particular animus re GONDOLIERS, so not all that cognizant about it all.
I too love parodies!